Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors

A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm x 1.4 mm pads arranged in a 32 x 16 array. The silicon detectors were located edgewise on opposite sides and flanked by two non-position sensitive BGO detectors. The scanner performance was measured for its sensitivity, energy, timing, spatial resolution and resolution uniformity. Using the experimental scanner, energy resolution for the silicon detectors is 1%. However, system energy resolution is dominated by the 23% FWHM BGO resolution. Timing resolution for silicon is 82.1 ns FWHM due to time-walk in trigger devices. Using the scattered photons, time resolution between the BGO detectors is 19.4 ns FWHM. Image resolution of 980 microm FWHM at the center of the field-of-view (FOV) is obtained from a 1D profile of a 0.254 mm diameter (18)F line source image reconstructed using the conventional 2D filtered back-projection (FBP). The 0.4 mm gap between two line sources is resolved in the image reconstructed with both FBP and the maximum likelihood expectation maximization (ML-EM) algorithm. The experimental instrument demonstrates sub-millimeter resolution. A prototype having sensitivity high enough for initial small animal images can be used for in vivo studies of small animal models of metabolism, molecular mechanism and the development of new radiotracers.     

DRG 272: does it provide adequate burn center reimbursement for the care of patients with Stevens-Johnson syndrome and toxic epidermal necrolysis?

Patients with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TENS) often are referred to burn centers for wound and intensive care management. Unless they undergo a surgical procedure, patients with this diagnosis are assigned to DRG 272 to determine hospital reimbursement. In 2002, this DRG had an average length of stay of 5.2 days and an average national Medicare reimbursement of $4,416. The purpose of this study was to compare demographics, resource utilization, and hospital charges and reimbursement for all patients assigned to this DRG and to evaluate the effect of the extent of surface area involvement on resource utilization, hospital costs, and reimbursement. We reviewed the records of all patients admitted to our burn centers who were assigned to DRG 272 from January 1998 through December 2002. Patients with dermatologic diagnoses assigned to this DRG were compared with patients with SJS and TENS from our institutions and the American Burn Association National Burn Repository for calendar years 2000 and 2001. Patients assigned to DRG 272 with TENS involving >or=20% TBSA had significantly greater mortality, ventilator days, intensive care unit days, and length of hospital stay than patients with dermatologic conditions or SJS who were assigned to this DRG. In addition, patients with TENS had significantly greater hospital charges and costs than patients with dermatologic diagnoses and SJS. This study supports the need for a reassessment of the adequacy of DRG 272 for the reimbursement of burn center hospitals caring for patients with TENS. This would likely require modification of the current ICD-9-CM diagnosis codes to better quantify the extent of cutaneous involvement and the frequently associated comorbid conditions that accompany the cutaneous manifestations.     

Serial measurements increase the accuracy of laser Doppler assessment of burn wounds

Traditional methods of judging burn depth by clinical evaluation of the wound based on appearance and sensation remain in wide use but are subject to individual variation by examiner. In addition to the clinical difficulties with burn wound management, observer dependency of wound assessment complicates clinical trials of burn wound therapy. A laser Doppler flowmeter with a multichannel probe was used to measure burn wound perfusion as a tool to predict wound outcome. Serial measurement with laser Doppler flowmetry had an 88% specificity and a positive predictive value of 81% for identifying nonhealing wounds. These results suggest that laser Doppler flowmetry is a potentially useful tool for burn wound assessment.     

Haemangiopericytoma of the hard palate

Haemangiopericytoma is an aggressive vascular tumour with a high propensity for recurrence and metastasis. It typically occurs in the soft tissues of the extremities and trunk, and is rarely seen in the oral cavity. A case of haemangiopericytoma of the hard palate is presented. A 48-year-old woman presented with a gradually enlarging mass on the left side of her hard palate for 3 months. CT scans revealed a mass on the left side of the hard palate which extended to the nasal cavity and left maxillary sinus by causing erosion in the bones. Due to the possibility of local recurrence and occasional metastasis, a wide local excision was performed. There was no recurrence over 1 year's follow up.     

Twenty-six triplet pregnancies: a retrospective analysis

Methods  Twenty-six triplet pregnancies were delivered over 6 years. Results  Over 80% of pregnancies resulted after infertility treatment (21/26). Mean maternal age was 32. On average, the infants were delivered after 32 + 0 weeks; in 4 cases delivery was at <28 weeks. In 1 case, the leading triplet was delivered spontaneously, the remaining babies by Caesarean. Main indications for Caesarean were: premature membrane rupture, premature contractions, maternal hospitalisation for foetal lung maturation/tocolysis/antibiotics. Mean birth weights were (triplet I–III): 1,730, 1,630 and 1,550 g. Hydrops fetalis and renal agenesis resulted in IUFD of the leading triplet in two cases. All newborns were cared for by neonatology. Conclusions  Triplet pregnancies are challenging for all specialities involved. They should be managed from an early stage in cooperation with an experienced centre, allowing outpatient care for as long as possible if there are no complications. This also has a cost-reducing impact.     

Leptin in CAPD patients: serum concentrations and peritoneal loss.

BACKGROUND: To determine whether serum leptin concentrations in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) are influenced by peritoneal loss of leptin and to compare serum leptin levels of normal subjects with those of patients receiving renal replacement therapy such as haemodialysis (HD), CAPD, or kidney transplantation. SUBJECTS AND METHODS: Eighty-four individuals were investigated: six females and 14 males on standard CAPD; 13 females and 13 males on chronic HD; 10 female and eight male kidney transplant recipients, and 10 female and 10 male subjects as controls. Morning serum, 8-h and 24-h samples of peritoneal fluid concentrated to 6-20-fold by Centricon 3 (cutoff 3000 daltons), and 24-h urinary concentrations of leptin were measured with commercial RIA (Linco Research, Inc., USA). Venous blood and peritoneal fluid samples of albumin, beta2-microglobulin, glucose, urea, and creatinine were determined by standard laboratory techniques. Serum insulin levels were measured by radioimmunoassay. RESULTS: Patients (men and women) on CAPD and after kidney transplantation exhibited significantly higher serum concentrations of leptin and leptin/BMI ratios than control subjects. These increased values did not reach statistical significance in HD patients. Serum leptin concentrations were correlated very significantly with BMI in all cases (r=0.380, P<0.001). Moreover, in CAPD patients (r=0.630, P<0.007) and in HD patients (r=0.668, P<0.005), but not in kidney transplant recipients or control subjects, significant correlations were observed between serum leptin and insulin concentrations. Residual renal function (RRF) in the range 0-12.8 ml/min and serum beta2-microglobulin levels in the range 7.9-47.1 mg/l did not influence serum leptin levels in CAPD and HD patients. As expected, leptin was detected in the peritoneal fluid of CAPD patients. Twenty-four-hour peritoneal loss (30.95+/-21.05 ng/min) and 24-h peritoneal clearance (0.01+/-0.01 ml/kg/min) of leptin account for only 3.9% of estimated whole-body leptin production rate and 0.7% of leptin clearance from plasma respectively. Twenty-four-hour urinary losses of leptin in CAPD patients were negligible, accounting for 5.6+/-1.8% (range 0.3-15.2%) of total (peritoneal and urinary) loss of this hormone. CONCLUSIONS: These findings suggest that serum leptin levels are not affected by continuous peritoneal loss of leptin during CAPD and that insulin resistance and hyperinsulinaemia contribute to elevated serum leptin concentrations in CAPD and HD patients. The aetiology of increased serum leptin levels in kidney transplant recipients is probably different from that in dialysis patients.     

Elevated lipid levels in Vietnam veterans with chronic posttraumatic stress disorder.

BACKGROUND: Elevated cholesterol levels have been reported in panic disorder and anger attacks, but not major depression. No data have been reported in posttraumatic stress disorder (PTSD). METHODS: Seventy-three male Vietnam veterans with chronic (PTSD) had serum lipid screening upon entry to a 90-day inpatient program. RESULTS: Elevated cholesterol, low-density lipoprotein, triglycerides, and reduced high-density lipoprotein, were frequent in Vietnam veterans with chronic PTSD and are significant risk factors for coronary artery disease. CONCLUSIONS: Routine lipid screening may be warranted in this at-risk population. Altered lipid levels may result from activation of the noradrenergic system.